1. Field of the Invention
The present invention relates to an image-forming device such as a laser printer, and to a process cartridge detachably provided in the image-forming device.
2. Description of the Related Art
Generally, laser printers and other electrophotographic image-forming devices are provided with a photosensitive drum for carrying a developer image, and a transfer roller disposed in contact with the photosensitive drum for attracting the developer image with a transfer bias applied to the transfer roller. When a sheet of paper passes between the photosensitive drum and the transfer roller, the developer image migrates toward the transfer roller and is transferred onto the paper, forming an image thereon. However, when the paper is separated from the photosensitive drum at a position upstream of a transfer position between the photosensitive drum and the transfer roller with respect to the paper-conveying direction, a pre-transfer may occur in which an electric field produced between the paper and the photosensitive drum causes developer to scatter from the photosensitive drum onto the paper.
To resolve this problem, a guide plate has conventionally been provided on the upstream side of the transfer position for guiding the paper toward the photosensitive drum in order to suppress pre-transfer. This technology is disclosed in Japanese unexamined patent application publication No. 2003-5535.
However, when the guide plate is formed of a film or other flexible member in the technology described above, the guide plate bent by the paper returns to its original position and flaps when the trailing edge (upstream end) of the paper leaves the guide plate, potentially generating noise (referred to as “flapping”). Further, the guide plate must be separated a certain distance from the transfer position to prevent the guide plate from contacting and damaging the surfaces of the photosensitive drum and the transfer roller. Accordingly, when the trailing edge of the paper passes over the edge of the guide plate, the trailing edge is no longer supported by the guide plate and can flap in the space between the transfer position and the guide plate. Such flapping in the trailing edge of the paper may cause problems in transferring developer, leading to a drop in quality of the images formed on paper.